No. If they mean it they need to show it before I would believe what comes out of there mouths again it would take time. As the old saying goes if you are going to talk the talk then need to walk the walk.
No, if someone stole something from you, but said they wouldn't do it again, you'd be an idiot to leave them alone with your stuff. The same idea works with cheaters. You consciously decide to cheat on someone, it can not be an accident. If they willfully did it the first time, chances are they will do it again.